A press-fit terminal is an acicular terminal having compressive elasticity, and is press-fitted into a through-hole formed in a substrate, to ensure a frictional force (retaining force), thereby being mechanically and electrically fixed to the substrate. A copper-plated electrode portion is formed on an inner circumferential surface of a conventional through-hole. The electrode portion contributes to a retaining force between the through-hole and a press-fit terminal pin. A male connector (plug connector) is attached to the press-fit terminal fixed to the substrate, and is fitted to a female connector (receptacle connector), thereby establishing electrical connection. The surface of a terminal for the press-fit terminal is mainly subjected to Sn plating in order to improve a contact property with a through-hole of a connection substrate in light of lead free.
This press-fit terminal connects a connection terminal and a control substrate without performing conventional soldering. It is not assumed that the press-fit terminal once inserted into the through-hole is extracted from the through-hole again. Therefore, as a matter of course, a person cannot insert the terminal for the press-fit terminal into the through-hole with a hand. For example, when the terminal for the press-fit terminal is inserted into the through-hole, a normal force of 6 to 7 kg (60 to 70 N) per terminal is required. A significant pushing force is required in a connector subjected to molding, because 50 to 100 terminals are simultaneously used as the press-fit terminal.
For this reason, when the terminal for the press-fit terminal is inserted into the through-hole, the outer periphery of the press-fit terminal is subjected to a large welding pressure by the through-hole; comparatively soft Sn plating is shaven; and the shaven pieces are dispersed around, which disadvantageously causes short-circuit between the adjacent terminals depending on the case.
By contrast, a press-fit terminal inserted into a conductive through-hole of a substrate in a press-fit state is described in Patent Literature 1. In the press-fit terminal, at least a substrate inserting portion of the press-fit terminal is subjected to tin plating with a thickness of 0.1 to 0.8 μm, and the portion for which the tin plating is carried out is subjected to copper intermediate layer plating with a thickness of 0.5 to 1 μm and nickel base plating with a thickness of 1 to 1.3 μm, thereby to enable the suppression of the shaving of the tin plating.
A press-fit terminal is described in Patent Literature 2. In the press-fit terminal, a base plating layer made of Ni or a Ni alloy is provided on the entire surface of a base material. A Cu—Sn alloy layer and a Sn layer are sequentially provided on the surface of the base plating layer of the female terminal connection part of the base material, or a Cu—Sn alloy layer and a Sn alloy layer are sequentially provided on the surface. Alternatively, a Au alloy layer is provided on the surface. A Cu3Sn alloy layer and a Cu6Sn5 alloy layer are sequentially provided on the surface of the base plating layer of the substrate connection part of the base material, and Sn is not exposed on the surface of the Cu6Sn5 alloy layer. Thereby, the generation of shaving offscum of the Sn plating can be suppressed as compared with Patent Literature 1; and a synergistic effect obtained by providing the soft Sn layer or Sn alloy layer on the hard Cu—Sn alloy layer can improve a coefficient of friction to thereby weaken an inserting force when a terminal for press-fit is inserted into the through-hole.